Tourism can be bad for a tourist destination in a number of ways. These include:

Economics. If a region comes to depend too much on tourism, what happens if the tourists stop coming? If the country the tourists comes from has a recession, for example, the destination may be hurt badly if it has no other major industries to fall back on.

Environment. In areas that don't have large native populations, the influx of tourists can have negative impacts on the environment. On Oahu in Hawaii, for example, the tourist destination of Hanauma Bay was once badly harmed (up to the late 1980s) by the impact of too many tourists.

Cultural/societal. Too much tourism can make people of a destination feel as if they are on display for the pleasure of rich people from other countries. This can lead to negative attitudes about themselves and their society.